Inductive power transmission has many important applications across multiple industries and markets. FIG. 1 shows a conceptual representation of a conventional resonant inductive power transmission system. In FIG. 1, DC power supply 10, inverter 12, and resonating network 14 cooperate to provide a source of alternating electrical energy that is applied to the primary induction coil 16. Magnetic coupling between the primary induction coil 16 and a secondary induction coil 18 transfers energy to the secondary induction coil 18, which is removed by some distance from the primary induction coil 16. The primary and secondary induction coils 16, 18 constitute a loosely coupled air core transformer. Resonance applied to the primary induction coil 16 increases primary side inductor current producing a corresponding increase in the magnetic flux in the secondary inductor current and, therefore, in the power transferred from the primary to the secondary. The secondary inductor current is processed by a resonating network 20 and is rectified by a high-power rectifier 22 for application to DC load 24 in a conventional manner.
Efficient resonant inductive wireless power transfer requires that a significant portion of the magnetic flux lines emitted by the sending coil travel through the area contained by the perimeter of the receiving coil so as to maximize magnetic coupling. Axial coil misalignment significantly reduces coil-to-coil magnetic coupling and therefor detracts from efficient power transfer. Furthermore, axial coil misalignment alters coil inductance from expected design values leading to loss of resonance and additional power transfer inefficiencies.
Coil axial alignment errors are encountered routinely and present a critical problem for manufacturers of electric and electric-hybrid vehicles that require a wireless source of external source of power. It is desired to develop a system for charging vehicles that identifies the magnitude and direction of coil alignment error and provides steering information to a human driver or non-human apparatus in order that the vehicle may be positioned with minimal coil alignment error. The present invention addresses these needs in the art.